AUGH. I played X-2 through twice and never got this. Somebody just posted a youtube video showing a hidden Auron scene in X-2. You have to wait for Yuna and Rin to have a 6-minute conversation before getting to the sphere, but it's got a textbook Auron line. :)

SPOILERS, of course:

Edit: Brain freeze. I now expect Auron/Gippal smut from those better qualified to write such things. (Except you're all busy with XII.)